In a large bowl or with your stand mixer cream the granulated sugar and butter until it is fluffy. If using the stand mixer it will take about 5 minutes.
Once the sugar and butter is creamed together, add in the egg and vanilla extract.
In a medium sized bowl mix the flour, baking powder, salt. Use a whisk to mix everything together thoroughly.
Slowly add the flour mixture to the sugar, butter, egg and vanilla extract mixture. Mix everything until well incorporated.
Put half of the freshly made dough between two sheets of parchment paper and roll it out to 1/4 inch thick.
Repeat with the rest of the dough.
Put the rolled dough including the parchment paper, on a cookie sheet and refrigerate for 10 minutes or longer.
Your dough will be chilled and ready to cut and bake.
Repeat with scraps after cutting cookies.
Bake at 325° F for 10 -15 minutes. Let cool.
While the cookies are cooling make your Royal Icing.